Removing MySQL check from Makefile
Fixing a bug related to gaussian elimination + assumptions

When using assumptions, we ad a dummy decision level if the assumption
is already set. However, we forgot to call gaussian elimination
afterwards, so a level was skipped. This meant that in some cases, the
value of the matrix was not saved and chaos ensued
Some cleanup of the Gaussian Elimination routine
Adding some commented-out code to aid in debugging Gaussian elimination